114
edits
Conduction: Difference between revisions
Jump to navigation
Jump to search
no edit summary
No edit summary |
No edit summary |
||
| Line 53: | Line 53: | ||
[[Image:Surawicz.jpg|120px|thumb|right|Dr Surawicz, founder of the tangent method, still active in November 2006, at age 89.]] | [[Image:Surawicz.jpg|120px|thumb|right|Dr Surawicz, founder of the tangent method, still active in November 2006, at age 89.]] | ||
Although QT prolongation is potentially lethal, measurement of the QT interval by physicians is not standardized, | Although QT prolongation is potentially lethal, measurement of the QT interval by physicians is not standardized, since different definitions of the end of the T wave exist.<cite>Viskin</cite> Most QT experts define the end of the T wave as the intersection of the steepest tangent line from the end of the T-wave with the base line of the ECG.<cite>Lepeschkin</cite> This leads to the following stepwise approach: | ||
{| class="wikitable" width="800px" | {| class="wikitable" width="800px" | ||
| Line 67: | Line 67: | ||
|} | |} | ||
In a | In a pathological prolonged QT time, it takes longer than the normal amount of time for the myocardial cells to be ready for a new cycle. There is a possibility that some cells are not yet repolarized, but that a new cycle is already initiated. These cells are at risk for uncontrolled depolarization, induction of [[Torsade de Pointes]] and subsequent [[Ventricular Fibrillation]]. | ||
{| class="wikitable" width="800px" | {| class="wikitable" width="800px" | ||
| Line 74: | Line 74: | ||
| | | | ||
The QT interval is prolonged in congenital [[long QT syndrome]], but QT prolongation can also occur as a consequence of (a.o.): | The QT interval is prolonged in congenital [[long QT syndrome]], but QT prolongation can also occur as a consequence of (a.o.): | ||
* | * Medication (anti-arrhythmics, tricyclic antidepressants, phenothiazedes, for a complete list look on [http://www.torsades.org Torsades.org] | ||
* | * Electrolyte imbalances | ||
* | * Ischemia. | ||
QT prolongation is often treated with beta blockers. | QT prolongation is often treated with beta blockers. | ||
|} | |} | ||